Among exposure apparatuses, one is available which has a wafer stage and reticle stage for aligning a wafer and reticle by moving them at high speed, and which includes linear motors for driving the wafer stage and reticle stage. According to another exposure apparatus, a reticle is fixed, and a pattern is sequentially transferred to a plurality of shot regions by stepping a wafer. In these exposure apparatuses, to cope with heat generated by the coils of the linear motors, a fluoride solution is employed as a refrigerant. The refrigerant is supplied to portions in the vicinities of the coils of the linear motors, thus cooling the coils. The fluoride solution is widely utilized as a cooling medium because, e.g., 1) it has excellent electrical insulating properties, 2) it is completely inactive and does not attack a structural material such as a metal, plastic material, or rubber, and 3) it is incombustible.
Recently, the stage acceleration accompanying an increase in the process speed (throughput) increases more and more. As the sizes of the reticle and substrate increase, the stage mass also increases. Accordingly, the driving force defined by <mass of moving body>*<acceleration> becomes very large. The amount of heat generated by the linear motor for driving the stage also increases. The environmental influence of the generated heat is becoming apparent as an issue.
Conventionally, in the manufacturing process for a semiconductor element, e.g., an LSI or VLSI, formed to have a micropattern, a reduction projection exposure apparatus is used, which reduces and projects a circuit pattern formed on a mask onto a substrate coated with a photosensitive agent, and exposes it. As the integration density of the semiconductor elements increases, the pattern feature size decreases more and more, and accordingly high-accuracy alignment is required. Heat generated by the linear motor causes temperature increase or fluctuation in the stage space or in the vicinity of the linear motor where a mirror and the optical axis of an interferometer used in measurement for alignment are arranged. This decreases measurement accuracy of the interferometer.
To suppress problems resulting from the heat generated by the linear motor, the amount of coolant increases rapidly. A fluoride solution widely used as the cooling medium has a smaller heat capacity and a larger specific gravity than those of water. Thus, the amount of coolant increases, and the load on equipment, such as a pump, increases accordingly. Also, equipment, such as a heat exchanger, a transport pump, and the like, to be used, increase in size, leading to a very large cooling system.